Specifications

13. Calibrating for Digital Measurement
Page 94 USN52 L Operating Manual
NOTE: Recalibrate if a probe or wedge with a different
ANGLE or X-VALUE is put into use.
To disable angle beam flaw location and remove S=, P= and D=
from the measurement line, turn the ANGLE function (menu 9)
OFF:
,
13.9 TOF Mode - FLANK and PEAK
The TOF, time of flight function (lower level menus) determines
the way in which the USN52 L measures thickness or distance.
When TOF mode is set to FLANK, the measurement is deter-
mined by the point where each signal’s leading edge (flank) crosses
gate threshold level. In the A-scan, this corresponds to the inter-
section of the signal flank and gate bar.
When TOF is in PEAK mode, measurements are made to the
peaks (highest amplitude point) of the echo signals. If an echo
exceeds 127% screen height, measurement is made to the next
highest half-cycle peak.
Measurement accuracy in FLANK mode can be reduced if echo
signals vary greatly in amplitude. Therefore, PEAK is the preferred
mode for most applications, provided measurement echoes have
clearly defined peaks and remain under 127% screen height.
13.10 AUTOCAL Feature
The USN52 L provides an automatic calibration feature in which
the instrument calculates and performs the necessary adjust-
ments with minimal user intervention.
Access to the AUTOCAL feature is provided on the LOWER
LEVEL MENU: locate and highlight the AUTOCAL box. Pressing
turns on the AUTOCAL feature.
During the AUTOCAL feature, the operator will need to input two
reference thicknesses (S-REF1 and S-REF2) which will be deter-
mined by the test block(s) used. Default values for S-REF1 and
S-REF2 are 1.000 inch and 4.000 inch.
From the same LOWER LEVEL MENU where AUTOCAL is turned
ON, select “POSITIVE” in the GATE LOGIC box and “0 TO 1st” in
the MEASURE box. The TOF box can be set to either “PEAK” or
“FLANK.” Press the HOME key to access the UPPER LEVEL
MENUS and select the S-CAL position.